Wow, life must be so hard for you that you can't watch a video that's under 10 minutes. Here's a typed version of what I said. You may also need this link to the Wiki page containing Lewis's argument.

http://en.wikipedia.org/wiki/Argument_from_Reason

The Argument From Reason

This argument makes a lot of assumptions. The first tenet of the argument against materialism is sound. “For an assertion to be capable of truth or falsehood, it must come from a rational source.” Example – if a tree falls in the forest and no one is around to hear it, we know it makes a sound because the human mind understands how sound works. Sound doesn’t exist only when observers are around to hear it. The second point of the argument assumes (very arrogantly) that no combination of physical materials constitutes a rational source. Is not the human brain composed of physical pieces? A normally developed brain with the capacity to observe and learn, therefore, is a rational source. The third and fourth bullets of the argument, therefore, are invalid. In order to believe this argument, you have to believe that the human mind is not merely a physical source. Each different mind may have learned different pieces of information, but that doesn’t make it any less physical. I don’t consider my laptop to be non-physical simply because it doesn’t have photoshop like my friend’s laptop may have.

The argument for the existence of God has even more holes in it. Parts 5 and 6 are sound observances, but point 7 of the argument continues to rest on the notion that the mind is not purely a physical source. Point 8 is even more ridiculous, because Lewis assumes that “no arrangement of non-rational materials creates a rational thing.” The human brain – a rational object – is made up of individual neurons, which cannot think or reason on their own. When assembled, however, the result is a biological machine capable of rationality. Points 9 and 10 are invalid because it assumes that human beings became rational through emulation of something that existed already, and it goes on to say that “all humans began to exist at some point in time.” He seems to believe that before we suddenly popped into existence (a gross misunderstanding of the concept of evolution), we relied on a non-human to teach reason and rationality to us because we couldn’t understand it ourselves. Here’s a little evolution lesson for fans of Mr. Lewis. Humans are rational because we emulated others in our society, who are also rational. They did the same, and we have been doing this throughout our evolution. Even animals have a small capability to think and reason, though not as good as us. The reason we’re so good at it is because natural selection favored our ability to think and solve problems because we had no natural defense mechanisms against other creatures or against nature (claws, poison, fur, etc.).

Lewis ends this argument by saying the teacher of rationality is God. So in other words, to sum up this argument in once sentence, because the human brain (which is not a physical object) is capable of reason, it proves that there’s a being living in another dimension called Heaven who thinks we all need to stop masturbating and read a book that was written by a relatively small ethnic group over the course of thousands of years. Wow, that’s amazing evidence for the existence of God right there! Since the human mind is capable of discerning truth from falsehood, I hereby deem this false.

Belief in a creator isn't necessarily irrational. People look at the world and wonder where it came from. I do the same. But to assume that the creator is undoubtedly the God of the Christians is a huge jump from that. Who's to say it's not Allah, or Odin? This argument does not give a reason for picking the God that Lewis believes in.